Beyond Total Mesorectal Excision (TME)-Results of MRI-Guided Multivisceral Resections in T4 Rectal Carcinoma and Local Recurrence

Rectal cancer invading adjacent organs (T4) and locally recurrent rectal cancer (LRRC) pose a special challenge for surgical resection. We investigate the diagnostic performance of MRI and the results that can be achieved with MRI-guided surgery. All consecutive patients who underwent MRI-based multivisceral resection for T4 rectal adenocarcinoma or LRRC between 2005 and 2019 were included. Pelvic MRI findings were reviewed according to a seven-compartment staging system and correlated with histopathology. Outcomes were investigated by comparing T4 tumors and LRRC with respect to cause-specific survival in uni- and multivariate analysis. We identified 48 patients with T4 tumors and 28 patients with LRRC. Overall, 529 compartments were assessed with an accuracy of 81.7%, a sensitivity of 88.6%, and a specificity of 79.2%. Understaging was as low as 3.0%, whereas overstaging was 15.3%. The median number of resected compartments was 3 (interquartile range 3-4) for T4 tumors and 4 (interquartile range 3-5) for LRRC (p = 0.017). In 93.8% of patients with T4 tumors, a histopathologically complete (R0(local)-) resection could be achieved compared to 57.1% in LRRC (p < 0.001). Five-year overall survival for patients with T4 tumors was 53.3% vs. 32.1% for LRRC (p = 0.085). R0-resection and M0-category emerged as independent prognostic factors, whereas the number of resected compartments was not associated with prognosis in multivariate analysis. MRI predicts compartment involvement with high accuracy and especially avoids understaging. Surgery based on MRI yields excellent loco-regional results for T4 tumors and good results for LRRC. The number of resected compartments is not independently associated with prognosis, but R0-resection remains the crucial surgical factor.

Biomechanical behavior of MRI-signal-inducing bone cements after vertebroplasty in osteoporotic vertebral bodies: An experimental cadaver study

BACKGROUND

Conventional water-free polymethylmethacrylate cements are not MRI visible due to the lack of free protons. A new MRI-visible bone cement was developed through the addition of a contrast agent and either a saline solution or a hydroxyapatite (Wichlas et al., 2010). The purposes of the study were to examine the influence of the two MRI-signal-inducing cements on the biomechanical behavior of cadaveric osteoporotic vertebral bodies after vertebroplasty and to compare the performance of the cements with conventional polymethylmethacrylate cement.

METHODS

Three different cements were used: standard polymethylmethacrylate cement and two modified MRI-signal-inducing cements that were mixed with either a 0.9% saline solution or a hydroxyapatite. The modulus of elasticity for the standard polymethylmethacrylate cement was 2040MPa, and the moduli for the MRI-signal-inducing cements that were mixed with a 0.9% saline solution and a hydroxyapatite were 1477 and 1225MPa, respectively. The lumbar vertebral bodies from nine osteoporotic spines (mean age=87 years, range=78-99 years) of female cadavers were examined. Three groups were formed: polymethylmethacrylate cement with saline solution (n=14), polymethylmethacrylate cement with hydroxyapatite (n=12) and polymethylmethacrylate cement (n=13). The vertebral bodies were biomechanically tested before and after vertebroplasty. Stiffness was chosen as the primary biomechanical parameter.

FINDINGS

The vertebral body stiffness was nearly two-fold greater after vertebroplasty, and this increase was statistically significant for every group. All the groups had similar vertebral body stiffness value before and after the vertebroplasty. The UNIANOVA test for multivariate analysis of variance showed no influence of lumbar level, injected cement volume and initial vertebral body stiffness.

INTERPRETATION

The elastic moduli of the cements appear to exert little influence on the biomechanical values when the cement is in the vertebral body. Based on the direct comparison with the classic polymethylmethacrylate cement, we believe that the implementation of such cements for MRI-guided vertebroplasties is feasible.